Glossary of Electrical Terms (S - Z)

Electrical Terms S - Z

Published: Friday, 08 March 2024

Following on from our articles from A – I and J - R, we will be looking at electrical terms from S – Z. 

This article is not intended to offer electrical installation advice. For any electrical problems or concerns, it is always advisable to seek independent professional assistance from a certified and qualified electrician.

Self - Induction

This energy regulator has the ability to be manually adjusted to a desired level and then kept there automatically. The temperature control on a cooker-hob is one common application; after a setting is chosen, the heating element will turn on and off automatically to maintain the preset.


A semiconductor is made of a substance, like silicon, that has neither good electrical or thermal conductivity. When the material is properly prepared with an additional electron, it turns negative, or n-type. The material will become positive, or p-type, if it is manufactured in a method that eliminates an electron from it. Transistors and diodes can be created from junctions created by combining semiconductors of the "p" and "n" types.


This phrase refers to the possible configurations of several circuit elements. For instance, a single-pole light switch that controls a lamp is linked in series with it. The method of connecting a d.c. machine in which the armature and field windings are connected in series can also be explained by the team.

Short - Circuit

When two or more live conductors come into contact with one another or are connected to one another by an outside source—such as an inadvertent drill bit through a cable—a short circuit problem results.


This phrase is typically used in reference to the process of joining a direct current motor's field windings. This method involves connecting the armature and field windings in parallel. 


This energy regulator has the ability to be manually adjusted to a desired level and then kept there automatically. The temperature control on a cooker-hob is one common application; after a setting is chosen, the heating element will turn on and off automatically to maintain the preset.

Sine Wave

A particular waveform that shows current, voltage, or power over time is called a sine wave. One whole waveform in a 50Hz single-phase A.C. supply corresponds to a time interval of 20 mS.

A solenoid

A magnetic field will be created around and via a wire coil that is uniformly wound around a cylinder and has electricity flowing through it. The solenoid serves as the foundation for the relay, contactor, and basic electric doorbell.


'Star' refers to the arrangement of the supply transformer, the (secondary) windings, or, if the motor is three-phase, the way the stator winding may be linked in three-phase A.C. distribution circuits or three-phase electric motors.

Star - Delta

This is a phrase used in relation to three-phase electric motor starting. The basic idea is that the motor stator windings are first connected in star configuration, which results in a lower voltage and allows the rotor to start turning. The rotor is then automatically reconnected to a delta connection, which does not connect the full three-phase supply voltage across them, after a predetermined amount of time, usually a few seconds depending on how quickly the rotor approaches full speed. At this point, the rotor is operating at its maximum speed.


Different electric motor starters are available based on the specific application that needs to be met. The Direct-On-Line (D-O-L), Star-Delta, or Auto-Transformer starter may be specified in the case of AC motors. A three- or four-terminal "Face-plate" starter would be utilised for DC motors.

The apparatus needed by low pressure mercury fluorescent luminaires to create an electrical discharge through the tube at startup may also be referred to as a "starter."


A three-phase electric motor's stator is the machine's fixed component. The stator windings are positioned inside the stator cylinder and are carried by or held in place by the stator. Via an appropriate starter, these windings are connected to the three-phase power supply.


This word refers to the speed at which a magnetic field inside an a.c. motor rotates inside the stator. The power supply frequency, which in the UK is 50 Hz, and the quantity of magnetic pole pairs formed when an alternating current flows through the stator windings determine the speed.

Note: Inside the stator, a single set of three-phase windings will produce a single pair of magnetic poles, or a North and a South polarity. There are more magnetic pole pairs the more winding sets there are. The goal of adding more pairs of poles is to increase the torque applied to the motor's drive shaft, enabling it to do more tasks.


A terminal is used to connect a conductor to an accessory or piece of equipment. A screw, clamp, push-on, soldered, or crimped lug connection are examples of terminals.


Testing is a process that uses specialised instruments to determine the state of a circuit, termination, or circuit component. Upon completion of an electrical installation, a battery of tests is carried out to ensure that the installation satisfies current regulations and adheres to the specifications specified in the original design. For the purpose of demonstrating compliance and for upcoming installation testing and inspection, a record of the test findings is maintained.


This resistor is sensitive to temperature; its design can be positive or negative, and it will alter resistance in response to variations in temperature.

Motor windings frequently have embedded positive temperature coefficient (PTC) thermistors. When the windings heat up excessively during operation, the thermistor's resistance rises, and a voltage drop results. Consequently, the motor starter control circuit will be opened, cutting off the motor's supply and guarding against winding damage.

When maintaining a cool or cold environment, the negative temperature coefficient (NTC) thermistor is utilised in air conditioning and refrigeration systems. When the temperature rises, the NTC resistance decreases, enabling the compressor to be turned on and subsequently bringing the temperature down.


when heat is delivered to the junction created by bonding two distinct metals that are in the shape of conductors together at one end. There will be a voltage created by the two metal conductors. The thermocouple can be used to gauge a furnace's temperature or in gas fire starting systems.


The thermostat is a device made of two different metals, such as brass and invar, that are fused together into the shape of a strip. Because the two metals are bound together, the expansion of the heated brass causes the strip to bend because it expands more quickly than the invar. When a set of contacts is integrated into the strip, the contacts can be adjusted to open or close as needed. 

By automatically turning the heating system on or off in response to temperature variations, the room thermostat used in residential central heating systems is intended to maintain the surrounding temperature.


Another name for thyristors is silicon-controlled rectifiers (SCRs). It's a regulated rectifier, a solid-state device. In contrast to a solid-state rectifier or diode, which continuously converts A.C. to D.C. when powered on, an SCR only functions when it is turned on by activating the device's "gate" connection. 


The phrase "earth" or "general mass of earth," or "Terra," is used to designate various supply systems in the United Kingdom, such as TN-S, TN-C-S, or TT.


The force used to rotate an electric motor.


A piece of stationary electrical equipment with windings positioned on steel limbs that have been laminated and are a part of a core frame. Transformers can be big, as in supply distribution systems, or small, as in individual electrical equipment pieces. Their purpose is to increase or decrease voltages.

Note: These days, electrical equipment more often contains electronic transformers. 


A solid-state component that amplifies voltage or current in electrical circuits.


"Apparent power" refers to the power in an alternating current circuit used to power a motor or other inductive load in which a magnetic field is created by current.


Tungsten comes in the form of a wire that has a high resistance and can incandesce when current is applied to it to produce light in a vacuum. The standard example is the tungsten filament lightbulb.

Trainee Electrician


Uninterruptible Power Supply (UPS)

In the event that the building's main power source fails, this battery supply has the ability to immediately take over a portion of the connected electrical load. To maintain the supply of power to computers and other vital devices that need a steady supply, the D.C. battery supply is electronically converted into an A.C.



The volt is a measure of electromotive force, or E.M.F, which can be generated thermally on a thermocouple, chemically in a battery, or magnetically in a generator or alternator. Symbol: V or U.


A voltmeter is a type of measurement device that can be used to establish the voltage between two locations in a circuit that have different potentials, such as the positive and negative of a battery source or the line and neutral of a single-phase A.C supply. A voltmeter can have an electro-mechanical design, such as a moving iron for alternating current or direct current, a moving coil for direct current only, or a digital design.



The unit of measurement for power is the watt. W is the symbol.


This measurement tool illustrates a circuit's actual power. Typically, the device has three connectors, which enable it to be linked in parallel for voltage measurement and series for current measurement. The power of the circuit or load is shown by the combined influence of the magnetic fields generated in the current and voltage coils of the instrument.

Wiring Diagram

This schematic diagram exhibits all of the conductors in a circuit, including the protective conductor and all of the equipment, accessories, and components.


Xeon (XE)

This inert gas is used to fill specific kinds of light bulbs and fluorescent tubes.


Some items appear transparent because of electromagnetic radiation with a shorter wavelength than light, which can pass through some objects but not others.



The laminated steel upright limbs of a power transformer are mechanically connected to form a metallic magnetic circuit that allows alternating magnetic flux to flow through it by the yoke, which is a laminated steel horizontal part.

Note: The transformer windings or coils are supported by the limbs.


Zenor Diode

This solid-state device is intended to function as a voltage regulator or limiter by being linked in parallel across a load. Because of its shunt connection, the zenor diode is reversed biassed, meaning that although it cannot conduct, it will short circuit and conduct when the voltage reaches a certain point.

The gadget bears the name of C. M. Zenor, who invented it.

We hope you have found our list of glossary terms helpful, and that it will serve as a helpful resource for you as you continue your studies as an apprentice in electrical engineering. 

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